In the conventional technology, polysilicon (Poly-Si) is mainly used as an electrode material which is formed on a silicon substrate. As a gate insulation film provided between the silicon substrate and the polysilicon electrode material, a silicon oxide (SiO2), a silicon oxynitride (SiON), and a silicon nitride (Si3N4) are used. As a related matter, in order to increase the capacity (proportional to ∈/d, where e is relative permittivity, and d is film thickness) of the gate insulation film, the thickness of the gate insulation film (SiO2 (∈=3.9)) is conventionally reduced.
According to Japanese Laid-Open Patent Application No. 2000-294550, a method is disclosed wherein a gate insulation film having an equivalent oxide thickness of 1 nm or less is provided by performing an oxidation, nitriding, and oxynitriding directly on the surface of the wafer W by plasma processing.
There is a limitation to reducing the thickness of the gate insulation film; however, a method is presently suggested wherein the physical thickness of the layer can be increased to a certain extent by using a material having a high relative permittivity (High-K, where K is an equivalent to ∈).